Use of ceramics in the form of high temperature operating articles, such as components for power generating apparatus including automotive engines, gas turbines, etc., is attractive based on the light weight and strength at high temperatures of certain ceramics. One typical component is a gas turbine engine strut. However, monolithic ceramic structures, without reinforcement, are brittle. Without assistance from additional incorporated, reinforcing structures, such members may not meet reliability requirements for such strenuous use.
In an attempt to overcome that deficiency, certain fracture resistant ceramic matrix composites have been reported. These have incorporated fibers of various size and types, for example long fibers or filaments, short or chopped fibers, whiskers, etc. All of these types are referred to for simplicity herein as "fibers". Some fibers have been coated, for example with carbon, boron nitride, or other materials, applied to prevent strong reactions from occurring between the reinforcement and matrix. Inclusion of such fibers within the ceramic matrix was made to resist brittle fracture behavior.
Reported methods for final consolidation of ceramic matrix composites have included hot mechanical pressing or hot isostatic pressing techniques applied to a preform of ceramic matrix and reinforcing fiber in a shaped, heated die or in a high pressure, high temperature autoclave. Such techniques generally require that the matrix include liquid phases or sintering aids to allow the matrix material to flow around the reinforcing fiber architecture. Such techniques are expensive as well as time consuming and rely on intricate, complex equipment for the production of such ceramic matrix composites.
Other techniques, for example chemical vapor deposition or polymer precursor decomposition, do not require liquid phases as sintering aids. They rely on open porosity of the fiber structure for the transfer of the matrix materials throughout the reinforcing arrangement. In all of these known techniques, long times are required for such infiltration and generally at least about 8-20% porosity results.